RFID tags with bumped substrate, and apparatuses and methods for making

ABSTRACT

Radio Frequency Identification (RFID) tags are provided, along with apparatuses and methods for making. In some embodiments, the RFID tags include an RFID tag chip that is attached to an inlay and/or a strap. The inlay or strap has one or more contact bumps formed thereon. In some of these embodiments, the RFID tag chip includes pads for electrical contacts, but not chip-bumps, thanks to the contact bump.

CLAIM TO PRIORITY

This application claims priority from U.S.A. Provisional ApplicationSer. No. 60/997,493, filed on Oct. 3, 2007, the disclosure of which ishereby incorporated by reference for all purposes.

BACKGROUND

Radio Frequency IDentification (RFID) systems typically include RFIDtags and RFID readers. RFID readers are also known as RFIDreader/writers or RFID interrogators. RFID systems can be used in manyways for locating and identifying objects to which the tags areattached. RFID systems are particularly useful in product-related andservice-related industries for tracking objects being processed,inventoried, or handled. In such cases, an RFID tag is usually attachedto an individual item, or to its package.

In principle, RFID techniques entail using an RFID reader to interrogateone or more RFID tags. The reader transmitting a Radio Frequency (RF)wave performs the interrogation. The RF wave is typicallyelectromagnetic, at least in the far field. The RF wave can also bepredominantly electric or magnetic in the near field. The RF wave mayencode one or more commands that instruct the tags to perform one ormore actions.

A tag that senses the interrogating RF wave responds by transmittingback another RF wave. The tag generates the transmitted back RF waveeither originally, or by reflecting back a portion of the interrogatingRF wave in a process known as backscatter. Backscatter may take place ina number of ways.

The reflected-back RF wave may further encode data stored internally inthe tag, such as a number. The response is demodulated and decoded bythe reader, which thereby identifies, counts, or otherwise interactswith the associated item. The decoded data can denote a serial number, aprice, a date, a destination, other attribute(s), any combination ofattributes, and so on. Accordingly, when a reader reads a tag code, datacan be learned about the associated item that hosts the tag, and/orabout the tag itself.

An RFID tag typically includes an antenna system, a radio section, apower management section, and frequently a logical section, a memory, orboth. In earlier RFID tags, the power management section included anenergy storage device, such as a battery. RFID tags with an energystorage device are known as active or semi-active tags. Advances insemiconductor technology have miniaturized the electronics so much thatan RFID tag can be powered solely by the RF signal it receives. SuchRFID tags do not include an energy storage device, and are calledpassive tags.

BRIEF DESCRIPTION OF THE DRAWINGS

The following Detailed Description proceeds with reference to theaccompanying Drawings.

FIG. 1 is a block diagram of components of an RFID system according toembodiments.

FIG. 2 is a diagram showing components of a passive RFID tag, such as atag that can be used in the system of FIG. 1.

FIG. 3 is a section view showing how a bumped RFID tag chip can contactan antenna element in a tag made according to prior art.

FIG. 4A is a diagram showing some components for making an RFID tagaccording to embodiments.

FIG. 4B is a flowchart for illustrating a method for assembling an RFIDtag according to embodiments, for example using the components of FIG.4A.

FIG. 5A is a diagram for showing a basic relationship of how thecomponents of FIG. 4A can be arranged, according to an embodiment wherethe substrate is an inlay.

FIG. 5B is a diagram for showing a basic relationship of how thecomponents of FIG. 4A can be arranged, according to an embodiment wherethe substrate is a strap for placement on an inlay.

FIG. 6A is a section view showing an RFID tag made according to anembodiment where a bumped RFID tag chip is used.

FIG. 6B is a section view showing an RFID tag made according to anembodiment where an RFID tag chip advantageously does not need to bebumped.

FIG. 6C is a section view showing an RFID tag made according to anotherembodiment where an RFID tag chip advantageously does not need to bebumped, and contact bumps of the substrate are used as spacers.

FIG. 6D is a section view showing an RFID tag made according to one moreembodiment.

FIG. 7A is a diagram for illustrating that an antenna element can be aconductive trace that is formed continuously with the remainder of anantenna of the RFID tag according to embodiments.

FIG. 7B is a diagram for illustrating that an antenna element can be aconductive trace that is separately connected to the remainder of theantenna of the RFID tag, according to embodiments.

FIG. 8A is a top view of a portion of an RFID tag according to a sampleembodiment.

FIG. 8B is a section view of the portion of FIG. 8A.

FIG. 9 is a high-level block diagram of a part of an RFID tagmanufacturing apparatus according to embodiments.

10A, 10B, 10C are snapshots of successive positions of an embossingapparatus according to an embodiment, to illustrate its operation.

FIG. 11 is a conceptual view of an embossing apparatus with a heatsource according to an embodiment.

FIG. 12 is a conceptual view of an embossing apparatus according toanother embodiment.

FIG. 13 is a flowchart illustrating an RFID tag manufacturing methodaccording to embodiments of the invention.

DETAILED DESCRIPTION

The present invention is now described. While it is disclosed in itspreferred form, the specific embodiments of the invention as disclosedherein and illustrated in the drawings are not to be considered in alimiting sense. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. Indeed, it should bereadily apparent in view of the present description that the inventionmay be modified in numerous ways. Among other things, the presentinvention may be embodied as devices, methods, software, and so on.Accordingly, the present invention may take the form of an entirelyhardware embodiment, an entirely software embodiment, an entirelyfirmware embodiment, or an embodiment combining aspects of the above.

As it has been mentioned, the present invention provides for RFID tagmanufacturing apparatus and methods. The invention is now described inmore detail.

FIG. 1 is a diagram of components of a typical RFID system 100,incorporating aspects of the invention. An RFID reader 110 transmits aninterrogating Radio Frequency (RF) wave 112. RFID tag 120 in thevicinity of RFID reader 110 may sense interrogating RF wave 112, andgenerate wave 126 in response. RFID reader 110 senses and interpretswave 126.

Reader 110 and tag 120 exchange data via wave 112 and wave 126. In asession of such an exchange each encodes, modulates, and transmits datato the other, and each receives, demodulates, and decodes data from theother. The data is modulated onto, and demodulated from, RF waveforms.

Encoding the data in waveforms can be performed in a number of differentways. For example, protocols are devised to communicate in terms ofsymbols, also called RFID symbols. A symbol for communicating can be adelimiter, a calibration symbol, and so on. Further symbols can beimplemented for ultimately exchanging binary data, such as “0” and “1”,if that is desired. In turn, when the waveforms are processed internallyby reader 110 and tag 120, they can be equivalently considered andtreated as numbers having corresponding values, and so on.

Tag 120 can be a passive tag or an active or semi-active tag, i.e.having its own power source. Where tag 120 is a passive tag, it ispowered from wave 112.

FIG. 2 is a diagram of an RFID tag 220, which can be the same as tag 220of FIG. 2. Tag 220 is implemented as a passive tag, meaning it does nothave its own power source. Much of what is described in this document,however, applies also to active tags also.

Tag 220 is formed on a substantially planar inlay 222, which can be madein many ways known in the art. Tag 220 includes an electrical circuit,which is preferably implemented in an integrated circuit (IC), the IC isreferred to in this document as RFID tag chip 224. The RFID tag chip isarranged on inlay 222.

In some embodiments in order to interconnect the relatively small RFIDtag chip with antennas an intermediate structure (not shown) may be usedin the RFID inlays. These structures are variously called “interposers”,“straps”, and “carriers” to facilitate inlay manufacturing. Interposersinclude conductive leads or pads that are electrically coupled to thecontact pads of RFID tag chip 224 for connecting to an antenna.

Tag 220 also includes an antenna for exchanging wireless signals withits environment. The antenna is usually flat and attached to inlay 222.RFID tag chip 224 is electrically coupled to the antenna via suitableantenna ports (not shown in FIG. 2).

The antenna may be made in a number of ways, as is well known in theart. The antenna pattern is formed from a conductive material. In theexample of FIG. 2, the antenna is made from two distinct antennasegments 227, which are shown here forming a dipole. Many otherembodiments are possible, using any number of antenna segments.

In some embodiments, an antenna can be made with even a single segment.Different points of the segment can be coupled to one or more of theantenna ports of RFID tag chip 224. For example, the antenna can form asingle loop, with its ends coupled to the ports. It should be rememberedthat, when the single segment has more complex shapes, even a singlesegment could behave like multiple segments at the frequencies of RFIDwireless communication.

In operation, a signal is received by the antenna, and communicated tothe RFID tag chip. The RFID tag chip both harvests power, and respondsif appropriate, based on the incoming signal and its internal state. Inorder to respond by replying, the RFID tag chip modulates thereflectance of the antenna, which generates the backscatter from a wavetransmitted by the reader. Coupling together and uncoupling the antennaports of the RFID tag chip can modulate the reflectance, as can avariety of other means.

In the embodiment of FIG. 2, antenna segments 227 are separate from RFIDtag chip 224. In other embodiments, antenna segments may alternately beformed on RFID tag chip 224, and so on.

FIG. 3 is section view 300 that shows how a bumped RFID tag chip 324contacts an antenna element according to the prior art. RFID tag chip324 is called bumped because it includes electrically conductivechip-bumps 326 attached to electrically conductive pads 325. Chip-bumps326 are electrically connected to a circuit in RFID tag chip 324. Theycan be made from a number of materials, such as gold, nickel gold,solder, etc., and be called accordingly gold bumps, nickel gold bumps,solder bumps, etc.

RFID tag chip 324 is affixed to a substrate 322 via chip-bumps 326.Substrate 322 can be a strap or an inlay. In the embodiment of FIG. 3,substrate 322 is an inlay, which has formed thereon two antenna elements327. Chip-bumps 326 are connected to one or more antenna elements 327.This way, a signal that is received wirelessly via antenna elements 327is guided to RFID tag chip 324.

In embodiments where substrate 322 is a strap, there would also be aninlay with the antenna elements thereon. Plus, there would be furtherelectrical connections between chip-bumps 326 and the antenna elements.

FIG. 4A is a diagram showing some components 420 for making an RFID tagaccording to embodiments. It will be understood that components 420, asshown, are not assembled into a final tag, but are discussedindividually. An economy is thus achieved in the present document, asindividual assemblies embodying the invention will be described later inthis document. It is further understood that components 420 may or maynot be all the components needed for constructing a final RFID tag.

Components 420 include an RFID tag chip 424. RFID tag chip 424 has oneor more pads 425. RFID tag chip 424 may or may not be bumped.Embodiments where there is no bumping are advantageous, because it willcost less to manufacture RFID tag chip 424.

Components 420 also include a substrate 422. In some embodiments,substrate 422 is an inlay. In other embodiments substrate 422 is a strapor carrier, intended for further attachment to an inlay. Substrate 422is called substantially planar, in that it can be considered lying alonga plane 442. If it is flexible, it can be manipulated to lie flat alongplane 442. Substrate 422 can be made from any suitable material topreserve the embossing. One such example is a thermoplastic material,especially where a heat source will be involved.

Substrate 422 has formed on it at least one bump 443, at a portion 446.The bump can be made as described later in this document. Bump 443 israised from plane 442. Bump 443 is called a contact bump, because it isintended to contact RFID tag chip 424. As will be seen, substrate 422can have additional bumps, for the same or different purposes.

Components 420 also include an antenna element 427. The nature ofantenna element 427 and its relationship to the whole RFID tag isdescribed in more detail later in this document. Antenna element 427 canadvantageously be formed on an inlay of the eventual RFID tag, whetherthe inlay is substrate 422, or not. Antenna element 427 is electricallycoupled to the pad. Coupling can be accomplished in many different ways,as will be described later in this document.

FIG. 4B is a flowchart 470 for illustrating a method for assembling anRFID tag according to embodiments, for example using the components ofFIG. 4A. Flowchart 470 does not show all the required operations. Moreoperations are described later in this document, explicitly orimplicitly. The operations of flowchart 470 can be performed in manydifferent ways. Some such ways are described later in this document.

According to an operation 474, a bump is formed on a substrate, whichcan be substrate 422. The bump can be raised from a plane of thesubstrate, as bump 443 is raised from plane 442. The bump can be calleda contact bump for reasons described above for bump 443.

According to an operation 476, an RFID tag chip is attached to thesubstrate such that it contacts the bump. The RFID tag chip can be thesame as RFID tag chip 424, or different. Attaching can be performed inany number of ways. In some embodiments, the RFID tag chip contacts thebump directly, for example with a proper adhesive, and so on. In someembodiments, the first contact bump has a layer on it, and the RFID tagchip contacts the bump via the layer. The layer can be conductive, aswill be seen later on, or be a dielectric, etc. Or, the adhesive can beconsidered such a layer, etc.

According to the method, a pad of the RFID tag chip becomes electricallycoupled to an antenna element. The antenna element can be the same asantenna element 427, or different. Coupling can be conductive orcapacitive, and can be performed in any number of ways, as will beappreciated from the further description. In some embodiments, couplingis inherent to the above described attachment. In other embodiments,additional operations are undertaken to effectuate the coupling.

FIG. 5A is a diagram for showing a basic relationship 521A of how thecomponents of FIG. 4A can be arranged. In relationship 521A, a substrate522A is an inlay that has two raised contact bumps 543A. An RFID tagchip 524A is on contact bumps 543A. An antenna element 527A is on inlay522A, and coupled with RFID tag chip 524A via its pads, which are notshown. There are a number of ways for this coupling, which are describedlater in this document.

FIG. 5B is a diagram for showing a basic relationship 521B of how thecomponents of FIG. 4A can be arranged. In relationship 521B, a substrate522B is a strap, which is provided on an inlay 523. Substrate 522B hastwo raised contact bumps 543B. An RFID tag chip 524B is on contact bumps543B. An antenna element 527B is on inlay 523, and coupled with RFID tagchip 524B via its pads, which are not shown. There are a number of waysfor this coupling, which are described later in this document.

More particular embodiments of the invention are now described. Thecomponents referred to below can be as was described above. In someembodiments, the one or more contact bumps become directly electricallyconnected with respective circuit pads. Two examples are now described.

FIG. 6A shows an RFID tag 620A made according to an embodiment. A bumpedRFID tag chip 624A has pads 625A, and chip-bumps 626A. A substrate 622Ahas contact bumps 643A. Antenna elements 627A are formed onto bumps643A. RFID tag chip 624A has been attached to substrate 622A such thatchip-bumps 626A contact bumps 643A. This embodiment achieves a largeseparation between the remainder of antenna element 627A and theremainder of the circuit of RFID tag chip 624A, as is desired. Still,this embodiment requires that RFID tag chip 624A be bumped.

FIG. 6B shows an RFID tag 620B made according to an embodiment. An RFIDtag chip 624B has pads 625B, but no chip-bumps. A substrate 622B hascontact bumps 643B. Antenna elements 627B are formed onto bumps 643B.RFID tag chip 624B has been attached to substrate 622B such that pads625B contact bumps 643B. This embodiment can achieve a satisfactoryseparation between the remainder of antenna element 627B and theremainder of the circuit of RFID tag chip 624B, as is desired. Plus,this embodiment advantageously does not require that RFID tag chip 624Bbe bumped, which is more economical.

In some embodiments, the one or more contact bumps become capacitivelycoupled with respective circuit pads. This can be performed as a resultof the shapes and the attaching. Two examples are now described.

FIG. 6C shows an RFID tag 620C made according to an embodiment. An RFIDtag chip 624C has pads 625C, but no chip-bumps. A substrate 622C has atop surface 681 and a bottom surface 682 that is opposite to top surface681. Substrate 622C has contact bumps 643C, which will be used asspacers. Antenna elements 627C are formed on top surface 681 ofsubstrate 622C, reaching regions 648C, but not contact bumps 643C. RFIDtag chip 624C has been attached to substrate 622C at top surface 681such that RFID tag chip 624C contacts contact bumps 643C. However, pads625C are only capacitively coupled with antenna elements 627C, withoutmaking a direct connection. More particularly, pads 625C are onlycapacitively coupled with regions 648C. Contact bumps 643C act asspacers that prevent antenna element 627C from contacting pads 625C.This embodiment can achieve a satisfactory separation between theremainder of antenna element 627C and the remainder of the circuit ofRFID tag chip 624C, as is desired. Plus, this embodiment advantageouslydoes not require that RFID tag chip 624C be bumped, which is moreeconomical. In addition, in this embodiment attaching will be easier,because the adhesion is not metal to metal at the top of bumps 643C.

FIG. 6D shows an RFID tag 620D made according to one more embodiment. AnRFID tag chip 624D has pads 625D, but no chip-bumps. A substrate 622Dhas a top surface 691 and a bottom surface 692 that is opposite to topsurface 691. Substrate 622D has contact bumps 643D, which will be usedas spacers. Antenna elements 627D are formed on bottom surface 692 ofsubstrate 622D, reaching the inside of bumps 643D. RFID tag chip 624Dhas been attached to substrate 622D at top surface 681 such that RFIDtag chip 624D contacts contact bumps 643D. However, pads 625D are onlycapacitively coupled with antenna elements 627D, without making a directconnection, through substrate 622D. Contact bumps 643D act as spacersthat further remove the remainder of antenna element 627D from theremainder of RFID tag circuit 624D to achieve a satisfactory separation.Plus, this embodiment advantageously does not require that RFID tag chip624D be bumped, which is more economical. In addition, in thisembodiment attaching will be easier, because the adhesion is not metalto metal at the top of bumps 643D.

In all of these examples, the RFID tag chip can be placed in anysuitable way. Some such ways include using a pick and place machine.Attachment can be realized by many processes, such as application ofanisotropic conductive paste, direct ultrasonic bonding, welding, etc.

The nature of the antenna elements of the invention, and theirrelationship to the antenna of the whole RFID tag, are now described inmore detail. Two examples are given, where the contact bumps areelectrically connected with the pads. In addition, the antenna elementsinclude conductive traces on the substrate at the contact bumps, such asis shown in 6A and 6B.

FIG. 7A is a diagram 749A according to an embodiment. A substrate 722Ahas a bump 743A. An antenna element 727A includes a conductive trace onthe substrate at the first contact bump. The conductive trace is formedcontinuously with a remainder of an antenna of the RFID tag, extendingmuch beyond the bump. An advantage is that at least a portion of antennaelement 727A can be manufactured by a single process, before or afterbump 743A is formed in substrate 722A.

FIG. 7B is a diagram 749B according to an embodiment. A substrate 722Bhas a bump 743B. An antenna element includes a conductive trace 727B onthe substrate at contact bump 743B. The remainder 728B of the antenna ofthe RFID tag is connected with conductive trace 727B via a differentconductor 729B. An advantage is that better focus can be given inmanufacturing conductive trace 727B on top of bump 743B.

These examples are not limiting. Parallel embodiments would be forembodiments where the contact bumps are only capacitively coupled withthe pads.

Bumps can be formed in the substrate in various shapes. Various methodsand machines for forming the bumps are described later in this document.Forming the bumps is sometimes also called embossing.

The dimensions of bumps can be as needed for the final assembly, forexample also considering the size of the RFID tag chip. In addition, thematerial properties of the substrate of the embossing, and for thesubstrate to retain the shape should also be considered. A height thatcan work well for contact bumps can be 15 μm to 20 μm. Moreover, for abump that is round, a sample diameter is 40 μm. Other dimensions canwork as well.

FIG. 8A is a top view of a portion 820 of an RFID tag according to asample embodiment. FIG. 8B is a section view of portion 820, along aline of FIG. 8A.

Referring first to FIG. 8A, portion 820 is on a substrate 822, which canbe an inlay or a strap as per the above. Substrate 822 has four contactbumps 843, on top of which there is an RFID tag chip 824. Pads of RFIDtag chip 824 are not shown, along with corresponding antenna elementsnear or on contact bumps 843. Those, if provided, might be alignedvertically in FIG. 8A away from contact bumps 843, so as to interfereminimally with the other features.

Examples have been given above where the bumps in the substrate arecontact bumps. Bumps can be used advantageously in the invention foradditional purposes. Two additional such purposes are now described,referring now also to FIG. 8B, together with FIG. 8A.

A first such purpose can be for alignment. Bumps can be formed on thesubstrate for aligning the RFID tag chip on the substrate, before theattachment. Such can be called alignment bumps. Sample alignment bumps844 are shown for portion 820. RFID tag chip 824 can be brought toalignment with contact bumps 843 by way of the chip being first broughtto contact with alignment bumps 844. If more than one alignment bumpsare formed, together they can form an alignment pocket for chip 824.Alignment bumps will improve the process, because they will improve thetolerance of placing chip 824 at exactly the intended location ofsubstrate 822.

Alignment bumps 844 preferably have a larger bump-height than contactbumps 843. A good difference is 15-20 μm.

In some embodiments, underfill 847 is applied between substrate 822 andRFID tag chip 824. Preferably, the underfill surrounds contact bumps843. Application of the underfill material can make RFID tag 820stronger and more robust.

A second purpose for bumping the substrate can be for containing theunderfill. In this example, raised containment bumps 845 are also formedon substrate 822 for containing underfill 847. Containment bumps 845 canbe in any desirable shape. Preferably they are elongated as shown, forexample to form a tub 848. Tub 848 can be 5 μm away from each side ofRFID tag chip 824. Containment need not be absolute. For example tub 848but might be leaky between adjacent containment bumps 845.

The invention also includes methods and apparatuses for manufacturingRFID tags, such as the RFID tags described above. General features ofthe inventive aspects of these apparatuses are now described, tocomplement what is already known about such apparatuses. In addition,some of the description that follows is to be understood with what hasalready been described. Examples are now described.

FIG. 9 is a high-level block diagram of a part of an RFID tagmanufacturing apparatus 900 according to embodiments. RFID tagmanufacturing apparatus 900 includes embossing apparatus 950 andattaching apparatus 960.

Embossing apparatus 950 can be used to emboss substrates such as inlaysor straps. Embossing apparatus 950 receives un-embossed substrate 922.The embossing process transforms substrate 922 to embossed substrate949, which has formed on it one or more raised bumps. The bumps are forthe purposes described above.

Attaching apparatus 960 forms RFID tag 920 from substrate 949 and anRFID tag chip 924. Attaching apparatus 960 includes a machine thatattaches an RFID tag chip 924 to embossed substrate 949. Attachment issuch that the RFID tag chip contacts one of the bumps, which is called acontact bump.

Embossing apparatuses can be made in any number of ways. They can be foreither forming multiple bumps concurrently to the substrate, or forforming a single bump. If for a single bump, in some embodiments theycan be used a number of times, to emboss multiple bumps in a singlesubstrate. In general, an embossing apparatus according to the inventioncan include a work support member that has a surface for receiving thesubstrate. In addition, a protruding member can press a portion of thesubstrate against a bumping-pattern. The bumping-pattern includes adepression to receive matingly the protruding member. This pressingforms the bump on the portion. In some embodiments, the protrudingmember protrudes from the surface, and the bumping-pattern is formedelsewhere. In other embodiments, the bumping-pattern is a depression inthe surface. Some examples are now described in more detail.

10A, 10B, 10C are snapshots of successive positions of an embossingapparatus 1050 according to an embodiment, to illustrate its operation.Apparatus 1050 receives a substrate 1022 for embossing.

As seen in FIG. 10A, embossing apparatus 1050 includes a work supportmember 1051. Work support member 1051 has a substantially flat surface1055 on which to receive a substrate 1022. A bumping-pattern 1053 isdisposed on surface 1055. Bumping-pattern 1053 includes one or moredepressions.

Embossing apparatus 1050 also includes a protruding member 1052.Bumping-pattern 1053 can receive protruding member 1052 matingly.Bumping-pattern 1053, along with protruding member 1052, defines thesize and location of features that will be embossed in substrate 1022.

As seen in FIG. 10B, substrate 1022 is moved over bumping-pattern 1053.Such moving can be performed by a feeder means (not shown). Protrudingmember 1052 moves in the direction of arrow A. This presses a portion ofsubstrate 1022 against bumping-pattern 1053. Pressing forms bump 1043 onsubstrate 1022.

As seen in FIG. 10C, protruding member 1052 moves back in the directionof arrow B. This releases embossed substrate 1022.

One or more bumps may be formed simultaneously or successively. If bump1043 is to include a conductive trace, the latter can be applied eitherbefore or after the embossing.

FIG. 11 is a conceptual view of an embossing apparatus 1150 according toan embodiment, which is an extension of the embodiment of FIGS. 10A,10B, 10C. Embossing apparatus 1150 includes a work support member 1151,a protruding member 1152, and a bumping-pattern 1153 that can receivematingly protruding member 1152.

In addition, embossing apparatus 1150 includes a heat source 1156 forheating a substrate (not shown). Heat source 1156 can be made in manyways, such as by a conductive heat source, etc. Heat source 1156 can bepart of work support member 1151, or it can be implemented as aradiating heat source (not shown) separate from support member 1151.Heat source 1156 is employed to elevate the temperature of a substratein conjunction with the embossing operation. Heating a thermoplasticsubstrate will soften it, which reduces the required pressure to performthe embossing operation. The lower pressure induces less stress in thesubstrate. In addition, heat may be used for the substrate to retain itsbumped shape.

FIG. 12 is a conceptual view of an embossing apparatus 1250 according toanother embodiment. Embossing apparatus 1250 includes two rotatingwheels 1251A, 1251B. Both of these have curved surfaces for receiving asubstrate 1222. Embossing wheels 1251A and 1251B are spaced apartsufficiently to allow substrate 1222 to pass through. Once substrate1222 is fed between the embossing wheels, it can be moved by them. Thesurface of one of these wheels, here that of 1251A, includes a bumpingpattern 1253. The surface of the other of these wheels, here that of1251B, includes a protrusion 1252 that is received matingly in bumpingpattern 1253. The surfaces can have additional features, etc.

Other embodiments are also possible. For example, a hybrid embossingapparatus can be made with surface 1051 of FIG. 10A being moved, andprotrusion 1252 being carried by a wheel such as wheel 1251B.

FIG. 13 is a flowchart that illustrates manufacturing methods 1300 ofRFID tag according to embodiments. Methods of 1300 may be practiced bydifferent embodiments, including but not limited to the apparatusesdescribed above.

At an optional operation 1371, a substantially planar substrate isreceived.

At an optional next operation 1372, the substrate is aligned to anembossing pattern for correct bump placement. Placement accuracy can be20 μm or less.

At an optional next operation 1373, the substrate is heated. If it ismade from thermoplastic material, a good range for the temperature is75-100° C.

At a next operation 1374, a contact bump is embossed, as per the above.

At a next operation 1375, an additional bump is embossed, as per theabove. In fact, operation 1375 can be repeated for all the desiredfeatures to be embossed.

At a next operation 1376, an RFID tag chip is attached to the substrate.

At optional next operation 1377, underfill is applied to fill a cavitybetween the RFID tag chip and the substrate. The underfill can be cured,etc.

Numerous details have been set forth in this description, which is to betaken as a whole, to provide a more thorough understanding of theinvention. In other instances, well-known features have not beendescribed in detail, so as to not obscure unnecessarily the invention.

The invention includes combinations and subcombinations of the variouselements, features, functions, and/or properties disclosed herein. Thefollowing claims define certain combinations and subcombinations, whichare regarded as novel and non-obvious. Additional claims for othercombinations and subcombinations of features, functions, elements,and/or properties may be presented in this or a related document.

The invention claimed is:
 1. A Radio Frequency Identification (RFID)strap, comprising: a substantially planar substrate with at least twocontact bumps and at least two alignment bumps, wherein the at least twoalignment bumps are raised from a plane of the substrate and do notoverlap with the at least two contact bumps; an RFID tag chip with atleast two pads, the tag chip aligned on the substrate by the alignmentbumps such that the pads electrically connect to the contact bumps; andleads formed on the substrate and electrically connected to the pads. 2.The RFID strap of claim 1, further comprising: a layer between the padsand the contact bumps such that the electrical connection is capacitive.3. The RFID strap of claim 1, in which the substrate has a top surfaceand a bottom surface opposite to the top surface, the tag chip contactsthe contact bumps at the top surface, and the leads are attached to thesubstrate at the bottom surface.
 4. The RFID strap of claim 1, in whichthe tag chip is secured to the substrate using underfill.
 5. The RFIDstrap of claim 4, in which the substrate further includes at least onecontainment bump for containing the underfill.
 6. The RFID strap ofclaim 4, in which the containment bump is elongated.
 7. The RFID strapof claim 1, in which the strap is attached to an inlay having an RFIDantenna.
 8. The RFID strap of claim 7, in which the leads areelectrically connected to the antenna.
 9. The RFID strap of claim 8, inwhich the electrical connection is capacitive.
 10. The RFID strap ofclaim 1, wherein the at least two alignment bumps are taller than the atleast two contact bumps.
 11. The RFID strap of claim 1, wherein the atleast two alignment bumps separate a surface of the tag chip from asurface of the substrate.
 12. A Radio Frequency Identification (RFID)strap, comprising: a substantially planar substrate with at least twocontact bumps and at least two alignment bumps raised from a plane ofthe substrate; an RFID tag chip with at least two pads, the tag chipaligned on the substrate by the alignment bumps such that the padselectrically connect to the contact bumps and the alignment bumps arepositioned outside a perimeter of the tag chip; and leads formed on thesubstrate and electrically connected to the pads.
 13. The RFID strap ofclaim 12, further comprising: a layer between the pads and the contactbumps such that the electrical connection is capacitive.
 14. The RFIDstrap of claim 12, in which the substrate has a top surface and a bottomsurface opposite to the top surface, the tag chip contacts the contactbumps at the top surface, and the leads are attached to the substrate atthe bottom surface.
 15. The RFID strap of claim 12, in which the tagchip is secured to the substrate using underfill.
 16. The RFID strap ofclaim 15, in which the substrate further includes at least onecontainment bump for containing the underfill.
 17. The RFID strap ofclaim 15, in which the containment bump is elongated.
 18. The RFID strapof claim 12, in which the strap is attached to an inlay having an RFIDantenna.
 19. The RFID strap of claim 18, in which the leads areelectrically connected to the antenna.
 20. The RFID strap of claim 19,in which the electrical connection is capacitive.
 21. The RFID strap ofclaim 12, wherein the at least two alignment bumps are taller than theat least two contact bumps.
 22. A Radio Frequency Identification (RFID)strap, comprising: a substantially planar substrate with at least twocontact bumps and at least two alignment bumps raised from a plane ofthe substrate; an RFID tag chip with at least two pads on a surface, thetag chip aligned on the substrate by the alignment bumps such that thepads electrically connect to the contact bumps and at least one of thealignment bumps contacts a side of the tag chip different from thesurface; and leads formed on the substrate and electrically connected tothe pads.
 23. The RFID strap of claim 22, further comprising: a layerbetween the pads and the contact bumps such that the electricalconnection is capacitive.
 24. The RFID strap of claim 22, in which thesubstrate has a top surface and a bottom surface opposite to the topsurface, the tag chip contacts the contact bumps at the top surface, andthe leads are attached to the substrate at the bottom surface.
 25. TheRFID strap of claim 22, in which the tag chip is secured to thesubstrate using underfill.
 26. The RFID strap of claim 25, in which thesubstrate further includes at least one containment bump for containingthe underfill.
 27. The RFID strap of claim 25, in which the containmentbump is elongated.
 28. The RFID strap of claim 22, in which the strap isattached to an inlay having an RFID antenna.
 29. The RFID strap of claim28, in which the leads are electrically connected to the antenna. 30.The RFID strap of claim 29, in which the electrical connection iscapacitive.
 31. The RFID strap of claim 29, wherein the at least twoalignment bumps are taller than the at least two contact bumps.